Wireless control networks have recently become a ubiquitous trend in the field of communication and connectivity/automation, especially for building management systems. Wireless technologies present major advantages in terms of freedom of device placement, device portability, and installation cost reduction, since there is no need for drawing cables and drilling. Thus, such technologies are particularly attractive for interconnecting, sensing, automation, control or monitoring systems using sensor devices such as light switches, light dimmers, wireless remote controllers, movement or light detectors, window or door openers, that have to be set up in distant places one from the other and from the devices they control, e.g. lights.
One of the drawbacks appearing in networks of the like relates to device powering. Indeed, since the devices are not wired, they can not receive power necessary for performing all the operations required in the network from the mains or via the connection with the controller. Thus, it has been envisaged to equip such devices with built-in batteries. However, since the devices are quite size-restricted, batteries may not be of a large size, which results either in a reduced device lifetime, or in labour intensive battery replacement.
It has been suggested to remedy this issue by equipping sensor devices with self-sustained energy sources that harvest energy from its environment or from the interaction with the user. Still, the amount of energy achievable by off-the-shelf energy harvesters is very limited, which means that the features and functions of the resource-restricted devices are heavily restricted.
Among the functions that are mandatory for good operation in a wireless network is the maintenance of correct communication, which makes it possible to ensure at any time that a resource-restricted device is linked to a router, also called proxy, which forwards messages on its behalf. In existing implementations therefore, a parent-child relationship is established between a device, generally resource-restricted, and its parent router. The child end device addresses all its communication to the parent for being forwarded to its final destination. However, especially in case of energy-harvesting device, this relationship creates a single point of failure in the network, because if the parent link is broken, communication from the end device can not be successfully performed anymore.
Several solutions have been suggested to remedy this problem, using proxy redundancy. A first type of solution aims at ensuring that, at any given time, one and only one proxy is forwarding frames on behalf of the resource-restricted device to the destination. However, the existing procedures of the like involve, for guaranteeing proxy redundancy, a large amount of additional communication, a large amount of additional proxy code, and considerable delay when a device moves in the network. Moreover, in these procedures, some prior master proxies may remain undiscovered, thus leading to many master conflicts.